//:C07:7.4:electric.c
#include <stdio.h>
#define RATE1    0.12589
#define RATE2    0.17901
#define RATE3    0.20971
#define BREAK1   360.0
#define BREAK2   680.0
#define BASE1    (RATE1 * BREAK1)
#define BASE2    (BASE1 + (RATE2 * (BREAK2 - BREAK1)))

int main(void)
{
    double kwh;
    double bill;

    printf("Please enter the kwh used.\n");
    scanf("%lf", &kwh);
    if(kwh <= BREAK1)
    {
        bill = RATE1 * kwh;
    }
    else if(kwh <= BREAK2)
    {
        bill = BASE1 + (RATE2 * (kwh - BREAK1));
    }
    else
    {
        bill = BASE2 + (RATE3 * (kwh - BREAK2));
    }

    printf("The charge for %.lf kwh is $%1.2f.\n", kwh, bill);
}